1. Technical Field
This invention relates generally a method and apparatus for the extraction of cannulated screws. More particularly, the instant invention relates to a method and apparatus for the extraction of a fractured, cannulated screw which has been fixated in bone.
2. History of Related Art
Many corrective surgical procedures involve the resection and subsequent fixation of bone. During the healing process, due to misdirected or excessive loading, the fixating screw, which is commonly cannulated, may be broken by a shearing action which occurs at the interface between the fixated surfaces.
The current state of technology encourages doctors in the surgical field to remove the fractured ends of the bone using a hollow boring drill and removing a large trephine of bone, with the broken internal fixation (i.e., screw) contained within the plug of bone so removed. This approach destroys a portion of the bone, and leaves a large defect within the patient that does not lend itself to easy refixation.
Some manufacturers have attempted to provide various retraction systems to grab the outside threads of a buried screw, usually on the surface of the bone, at the bone/screw interface, and then removing the screw by inducing a counter-clockwise rotation. However, this approach also tends to bore into the bone and several different sizes of retractors may be required to accomplish the task.
Further, if the fracture is not detected for some time, it is quite common for new bone growth to occur over and into the cavity formed by the cannula. This new growth must be removed to retrieve the fractured screw and such retrieval should be accomplished with a minimum of bone growth removal.
Therefore, what is needed is a retraction system for fractured, cannulated screws fixated in bone which does not require the removal of additional bone to retrieve the fractured internal fixation. Further, such a retraction system should allow for easy refixation, and accomplish the task with a minimum number of elements.
Finally, such a system should be easily accommodated by standard surgical power implements and operate to free the internal fixation from the bone even after new growth has entered into the cannulated area.